Hugo uses Chroma for code syntax highlighting. That is, when putting a code fence block into the Markdown source that is rendered by Hugo into a webpage, Hugo uses Chroma to highlight syntactical elements of the code similar to a modern IDE or Gist-like services, making the code more readable. Auto-detection of code languages is a computationally-intensive task, particularly for unlabeled code snippets. The webpage author specifies the code language using the Chroma alias.
For example, for Fortran or PowerShell scripts, the leading code fence is like: